Your draw length: you have another person help you. You take a full length arrow; or a long wooden dowel with a nock on it.
Then you close your eyes and draw back the arrow. Do this several times; and then draw and settle into where you feel comfortable.
Remember- eyes closed for this.
Then when your at your full draw; where you pull back to naturally; and where you find a good anchor for... have the friend mark the arrow shaft even with the back of the bow.
Then without looking; draw back twice more. You don't want to look and have that influence where you feel comfortable and locked into an anchor.
That distance gets marked on the shaft too.
Now open your eyes and measure the distance from the throat of the nock to the farthest marked spot down the shaft. Add a half inch ( this is where others can say the right distance) and that is your length for buying arrows.
Do it once with your eyes open and invariably you will try to pull back to far from your comfort zone. Your better off I think with a short draw; than a long one. Just my humble opinion; but do not despair if you are not pulling back as far as you thought you would.
Having all this right:
makes everything else so easy to figure out.